Inorganic glasses have been used in many applications by taking advantage of their excellent transparency, hardness, scratch resistance, weatherability, etc. They, on the other hand, have the defect of being brittle, easily broken and heavy. Organic glasses have the advantage of light weight, safety, resistance to breakage, processability, dyeability, etc., which the inorganic glasses do not possess. Polymethyl methacrylate, polycarbonate, diethylene glycol diallyl carbonate polymer, etc., have been used as the organic glasses. Particularly, in an eyeglass application, much is expected of the organic glasses because of their light weight, safety and resistance to breakage. Polystyrene (n.sub.D.sup.20 : about 1.59) and polycarbonate (n.sub.D.sup.20 : about 1.59) having a high refractive index are both thermoplastic polymers and are not molded by a casting method but by other methods such as injection molding. Hence, molding shrinkage tends to occur, and furthermore, they are unsuitable for producing a small quantity each of many kinds of articles as in lenses. Moreover, since these resins have poor heat resistance and solvent resistance, their uses, particularly as eyeglass lenses, are naturally limited.
On the other hand, the diethylene glycol diallyl carbonate polymer used in the production of lenses by the casting method has the defect that it has a low refractive index (n.sub.D.sup.20 : 1.499), and a lens made from it naturally has a larger thickness than that made from the inorganic glass. To remedy this defect, some methods for increasing the refractive index of resins have been proposed and disclosed in the prior art, for example, in Japanese Patent Application (OPI) Nos. 13747/1980, 61411/1981, 61412/1981, 2311/1982, 2312/1982, 23611/1982, 28115/1982, 28116/1982, 28117/1982 and 28118/1982 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application").
According to these prior techniques, the desired cured product is obtained by injecting a uniform mixture of a monomeric composition and a polymerization initiator into casting devices and subjecting it to polymerization over a long period of time. Thus, the casting devices cannot be efficiently used by rotation, and many casting devices are required. Furthermore, an enormous amount of heat energy is required for long-term polymerization (for example, as long as 10 hours for each molding cycle), and the productivity is very low.